Single-Couple Component of Far-Field Radiation from Dynamical Fractures
Single-Couple Component of Far-Field Radiation from Dynamical Fractures
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DOI：
10.1785/0120080288
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发表时间：
2009-05
影响因子：
3
通讯作者：
L. Knopoff;Yun‐tai Chen
中科院分区：
文献类型：
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作者：
L. Knopoff;Yun‐tai Chen
摘要本文重新考察了地震文献中的两个经典理论，即远场弹性位移与动力断层表面的滑动速度成正比，以及地震断层的动力面内滑动具有双偶体力等效。结果表明，如果断裂发生在有限厚度的断层上，并且在推进的裂纹尖端附近存在强度减弱带，则在体力等效中存在额外的单偶项，在远场位移中存在额外的项，它们与推进的减弱带应力降增加的时间速率成正比。我们还表明，单偶等效并不违反牛顿力学原理，因为单偶中的扭矩不平衡被断裂带内的旋转所抵消；因此，裂纹辐射扭矩波和旋转变形场。
Abstract We reexamine two canons of the seismological literature, that elastic displacements in the far field are proportional to slip velocities on the dynamical fault surface, and that dynamical in-plane slip on an earthquake fault has a double-couple body force equivalent. We show that if faulting takes place on a fault of finite thickness, and there is a strength-weakening zone near the advancing crack tip, there is an additional single-couple term in the body force equivalence and additional terms in the far-field displacement, which are proportional to the time rate of increase of stress drop in the advancing weakening zone. We also show that the single-couple equivalent does not violate principles of Newtonian mechanics because the torque imbalance in the single couple is counterbalanced by rotations within the fault zone; the crack therefore radiates torque waves and a rotational deformation field.